SOVIET PEACE ROLE REPORTED IN S. YEMEN

The Soviet Union was reported Thursday night to be seeking to play a mediator's role in a violent power struggle in Southern Yemen, one of its closest allies in the Arab world.

However, tribal uprisings in the countryside were said to be threatening to spread the battles.

Fierce fighting continued for a fourth day in Aden, the capital, according to the fragmentary reports coming out of the country. Most of the communications were still cut, leaving Southern Yemen isolated.

Merchant seamen in the harbor told their shipping agents of deafening blasts and balls of flame over the city, apparently from a burning ammunition dump.

The battles pitted hard-line Communists who are close to Moscow against the government of President Ali Nasser Mohammed Hassani, which is avowedly Marxist but has lately been seeking reconciliation with Southern Yemen's more conservative neighbors, Saudi Arabia, Oman and Yemen.

A meeting was said to be under way Thursday night in the Soviet Embassy between Hassani and rebel leaders in hopes of working out a deal.

According to an unconfirmed report, those at the meeting included four rebel leaders whom the state radio had announced on Sunday had been executed for plotting to assassinate Hassani and stage a coup.

As fighting continued, three senior government officials from Southern Yemen arrived in Moscow Thursday, presumably to discuss the fighting.

The Soviet press agency Tass reported that the three, Prime Minister Haider Abubakr Attas, Foreign Minister Abdel Aziz Dali, and Trade Minister Ahmed Obeid Fadhli, were met by Geidar A. Aliyev, a first deputy prime minister who is the member of the Politburo usually assigned to meet Middle East leaders.

There were reports from a number of sources, including several Arabic newspapers in the gulf, that fighting had spread to the tribal hinterlands and that armed Bedouins were making their way toward the capital in support of the rebels.

"It appears that fighting has spread to all six provinces," a Western diplomat in Sana, Yemen, said, referring to radio messages he had received from Aden. "In Aden, gunfire and rocket fighting has been raging between the two sides since dawn."